So Gmax can't render, why do I need to be able to render?

For Halo you don't, rendering just creates the high quality image of your work. Once you put your work in into the game, the engine is renders it real time.

Rendering is good to have for creating a nice display piece.
Edited by YakZSmelk on May 4, 2011 at 12:12 AM

Oh ok, so that's for making still photographs in the professional graphics world (here's a 3d diagram of the solar system etc.). So for games, it isn't of any use?

Render to Texture is nice when you're making models, but there's possibly a way for gmax users to do this too: http://cgkit.sourceforge.net/tutorials/baking/baking.html
I haven't tried it yet
There's also YafRay, with which gmax can do your standard image rendering: http://www.xzzy.org/halo/gmax_render/

Rendering is a good way to show other people your work. People would be more impressed if you render it, rather than taking a snapshot of your screen.

So, rendering for me is only of any use for Halo if I want my pictures of models to look pretty. Otherwise, it has absolutely any necessary use? Is it a simulation of how it will look in game? If I don't render, will I miss important geometry ugliness or ugly shadows that will show in game?

Actually, the halo game engine renders the environment in real-time so yea, the render is "a simulation of how it will look in game" but with a few constraints.

Rendering is also good at optimizing models by painting the details on textures so that you can minimize the number of polygons. Here is an example on how to do it in blender: http://www.blendercookie.com/2010/08/30/retopology-and-normal/
-Zekilk